Physicians commonly require blood samples to analyze blood constituents to facilitate the diagnosis of certain diseases and to monitor and follow the effects of treatments on a variety of parameters. In the past, blood samples were routinely drawn from patient's veins using needles and syringes; however, recently, blood samples are more commonly collected using a system of tubes that retains a vacuum and draws a specified amount of blood into them when connected to an intravenous line. The vacuum is maintained within the tube by the means of rubber stopper or the like. A needle attached to a syringe or another retaining device can be pushed through the rubber stopper to allow the vacuum to draw a blood sample into the tube. The vacuum not only assists in drawing the blood sample into the tube but helps retain the stopper in the tube for safe transport of the blood sample to a laboratory or other facility.
One commercially available vacuum sealed tube system that has found widespread use is available under the trade name BD Vacutainer® Blood Collection Tube from Becton Dickinson of Franklin Lakes, N.J. These tubes are plastic tubes and may or may not contain, in the interior thereof, an additive, often an anticoagulant that needs to be mixed with the blood sample. The type of additive that is within the tube is identified by the color and/or color pattern on the rubber stopper. Thus, for any given analytic test, the correct tube is selected that contains the desired additive. A chart is available to confirm that the additive contained in the tube is proper for the desired laboratory use as well as to determine the number of inversions that is necessary to mix the blood sample with the additive. The general process is that (1) the tube with the correct additive is selected; (2) the correct amount of blood is drawn into the tube which allows the vacuum in the tube to be nearly exhausted; and (3) the tube is inverted the number of times dictated on the mixing chart for proper mixing of the blood sample and additive. It will be appreciated that the BD Vacutainer® Blood Collection Tube is merely one exemplary type of vacuum sealed container that is suitable for use with the present invention and that there are a number of other types of vacuum sealed tubes that can be used with the present invention.
In terms of blood sampling techniques, the practice of removing the rubber stopper and releasing the vacuum, filling the tube with blood and replacing the stopper is highly discouraged since the vacuum is lost, the stopper may not remain in place and blood may disperse from the tube resulting in contamination. In addition, practice guidelines within hospitals, clinics and offices require that the stopper not be removed to place additional fluid or reactants into the tube.
However, there are a number of shortcomings with this practice and with the conventional vacuum sealed tube system blood collection techniques and equipment. More specifically, there are some applications that involve collecting samples that require a different stabilizing or diluting agent. Unfortunately, the construction of the above vacuum sealed container and the existing blood collection protocol do not permit or accommodate such need and as a result, there is a need for a system that permits collection of samples to measure the level of certain drugs in the blood where such application requires the introduction of a stabilizing agent in some cases. Under existing protocol concerning removal of the stopper, this type of application is not possible.
It is therefore desirable to provide a device that overcomes these disadvantages and permits a defined amount of fluid or other reactant material, such as a powder or gel, to be introduced into a vacuum sealed tube without releasing the vacuum.